[C:1]1([C:7]2([C:13]3[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=3)[CH2:11][CH2:10][NH:9][C:8]2=[O:12])[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.CC(C)([O-])C.[K+].Br[CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28]>O1CCCC1>[O:12]=[C:8]1[C:7]([C:1]2[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=2)([C:13]2[CH:14]=[CH:15][CH:16]=[CH:17][CH:18]=2)[CH2:11][CH2:10][N:9]1[CH2:26][C:27]([O:29][CH2:30][CH3:31])=[O:28]To a solution of the product from Example 1A (1.0 g, 4.21 mmol) in tetrahydrofuran (20 mL) was added potassium tert-butoxide (1.0 M in tetrahydrofuran, 6.3 mL, 6.3 mmol) via syringe under nitrogen followed by ethyl 2-bromoacetate (0.47 mL, 4.21 mmol). The reaction mixture was heated to 80° C. and stirred overnight. The reaction mixture was cooled to room temperature, concentrated, and then diluted with ethyl acetate. The organic layer was washed with water and brine, dried over magnesium sulfate, filtered, and concentrated. Silica gel chromatography eluting with ethyl acetate/hexane (20:80) gave the title compound. MS (DCI+) m/z 324.2 (M+H)+.
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